Deck 12: Black Holes

Question 1

The energy from the accretion disk around a black hole would show gravitational red shift due to its immense gravity and tidal distortion of space there.

Answer 1

True

Question 2

Special relativity predicts that light bends near dense objects.

Answer 2

False

Question 3

The mass range for neutron stars is

A) 0.08 to .4 solar masses.
B) 0.4 to 3 solar masses.
C) 1.4 to 3 solar masses.
D) 3 to 8 solar masses.
E) 6 to 11 solar masses.

Answer 3

1.4 to 3 solar masses.

Question 4

Black holes suck up all matter in sight.

Question 5

If something falls into a black hole, it remains intact until it reaches the event horizon.

Question 6

Any main sequence star over 25 solar masses will probably retain enough matter in its core after its type II supernova to make a black hole.

Question 7

Only neutrinos can go faster than the speed of light.

Question 8

Which of the following can actually escape from inside a black hole's event horizon?

A) Neutrinos
B) Electrons
C) Very high energy gamma-rays
D) Protons
E) None of the above

Question 9

An object increases in mass if it is moving rapidly compared to the observer.

Question 10

The curvature of spacetime around a black hole is so extreme that outward-going signals cannot escape.

Question 11

An accelerating frame of reference cannot be distinguished from a gravitational field.

Question 12

The Schwarzschild radius of a black hole is about 3 km per solar mass; it is amazingly linear over a wide range of masses.

Question 13

Very rapid time variations help establish the tiny size of many X-ray sources, showing they must be collapsed objects of some kind.

Question 14

The singularity of a black hole is where general relativity predicts the density to become infinite.

Question 15

Einstein received the Nobel Prize in physics for his work with general relativity.

Question 16

Black holes with masses greater than a million solar masses explain the extremely rapidly moving stars and gas in the cores of galaxies.

Question 17

According to general relativity, objects moved on curved paths due to the force of gravity.

Question 18

The escape speed for a black hole's event horizon is the speed of light.

Question 19

Material that falls into a black hole can be seen by the electromagnetic radiation it emits before it reaches the event horizon.

Question 20

Special relativity says that c, the speed of light, is the maximum velocity for both matter and energy in our universe.

Question 21

The observed slowing of a clock in the vicinity of a black hole is a prediction of

A) the Roche Limit.
B) Special relativity.
C) General relativity.
D) Stellar nucleosynthesis.
E) the Cosmological Principle.

Question 22

If light from a distant star passes close to a massive body, the light beam will

A) bend towards the star due to gravity.
B) continue moving in a straight line.
C) change color to a shorter wavelength.
D) slow down.
E) accelerate due to gravity.

Question 23

As a spaceship nears an event horizon, a clock on the spaceship will be observed

A) to run faster.
B) to stop.
C) to run slowly.
D) to run backwards.
E) to run the same as one on Earth.

Question 24

What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.
B) Gravity is directly proportional to the mass of the attracting body.
C) Gravity is inversely proportion to the radius of the body.
D) Gravity is the opposite of the electromagnetic force.
E) Gravity can affect only massive particles, not massless photons.

Question 25

Einstein earned the Nobel Prize for his

A) special theory of relativity.
B) general theory of relativity.
C) development of the equivalence of energy and matter, E = mc².
D) work on the particle nature of light.
E) contributions to the development of the fission bomb.

Question 26

The equivalence principle says that a person in an elevator that is in freefall feels the same acceleration as

A) a person in an elevator going up with an acceleration of g.
B) a person in space, far from any gravitational source accelerating at g.
C) a person in an elevator going down with an acceleration of g.
D) a person in space, far away from any gravitational source with no acceleration.
E) a person in orbit of Earth accelerating at g upward.

Question 27

The equivalence principle says that a person in an elevator that is in freefall feels the same acceleration as

A) a person in an elevator going up with an acceleration of g.
B) a person in space, far from any gravitational source accelerating at g.
C) a person in an elevator going down with an acceleration of g.
D) a person in space, far away from any gravitational source with no acceleration.
E) a person in orbit of Earth accelerating at g upward.

Question 28

An observer on a planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at

A) 0.25c.
B) 0.5c.
C) c.
D) 1.5c.
E) 2.5c.

Question 29

When observing an object, such as a space ship that is moving very quickly relative to you, the length of objects on that object will appear to be

A) longer than when they are at rest.
B) the same length as when they are at rest.
C) shorter than when they are at rest.
D) narrower than when they are at rest.
E) wider than when they are at rest.

Question 30

What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.
B) Gravity is directly proportional to the mass of the attracting body.
C) Gravity is inversely proportion to the radius of the body.
D) Gravity is the opposite of the electromagnetic force.
E) Gravity can affect only massive particles, not massless photons.

Question 31

In a vacuum, which form of electromagnetic radiation travels slowest?

A) Visible light
B) Radio
C) Gamma rays
D) Ultraviolet light
E) All forms of electromagnetic radiation travel at the same speed.

Question 32

Which of the following are attracted by gravity?

A) Antimatter
B) Any object with mass
C) Dlectromagnetic radiation
D) Neutrinos
E) All of the above

Question 33

The Schwartzschild radius for a 12 solar mass star is

A) 4 km.
B) 15 km.
C) 36 km.
D) 100 km.
E) 3000 km.

Question 34

As a spaceship's velocity gets closer to the speed of light

A) its length will increase and its clock will run more slowly.
B) its length will decrease and its clock will run faster.
C) its length will increase and its clock will run faster.
D) its length will decrease and its clock will run more slowly.
E) None of these will happen.

Question 35

What can we detect from matter that has crossed an event horizon?

A) Gamma-ray bursts
B) Radio waves if the matter was traveling fast enough
C) Visible light
D) X-rays if the matter was dense
E) Nothing

Question 36

What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.
B) Gravity is directly proportional to the mass of the attracting body.
C) Gravity is inversely proportion to the radius of the body.
D) Gravity is the opposite of the electromagnetic force.
E) Gravity can affect only massive particles, not massless photons.

Question 37

The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is

A) less than 1.0 solar masses.
B) greater than Schwartzschild's limit of 3 solar masses.
C) Chandrasekhar's limit of 1.4 solar masses.
D) between 1.4 and 2.0 solar masses.
E) greater than 25 solar masses.

Question 38

How are the event horizon and Schwarzschild radius related?

A) The Schwarzschild radius is smaller than the distance from the singularity of a black hole to the event horizon.
B) The Schwarzschild radius is equal to the distance from the singularity of a black hole to the event horizon.
C) The Schwarzschild radius is greater than the distance from the singularity of a black hole to the event horizon.
D) The size of the Schwarzschild radius is unrelated to the distance from the singularity of a black hole to the event horizon.
E) The size of the Schwarzschild radius is proportional to the distance from the singularity of a black hole to the event horizon.

Question 39

If the Sun were replaced by a one solar mass black hole

A) all terrestrial planets would fall in immediately.
B) we would still orbit it in a period of one year.
C) we would immediately escape into deep space, driven out by its radiation.
D) our clocks would all stop.
E) life here would be unchanged.

Question 40

If light from a distant star passes close to a massive body, the light beam will

A) bend towards the star due to gravity.
B) continue moving in a straight line.
C) change color to a shorter wavelength.
D) slow down.
E) accelerate due to gravity.

Question 41

What happens to the light that is emitted from the accretion disk around a black hole?

A) It is redshifted.
B) It is blueshifted.
C) It is pulled in multiple directions by tides.
D) It cannot be seen from anywhere in our solar system.
E) It is absorbed by the black hole.

Question 42

Why do scientists describe the theory of gravity as "incomplete"?

A) It does not incorporate a description of matter on a very small scale.
B) It does not explain why light bends near a dense object.
C) It does not agree with the expansion of the universe.
D) The gravity waves it predicts have not been observed.
E) It does not explain the effects on time from a massive object.

Question 43

In 1921, the Nobel Prize in physics was awarded to ________ for his work on the particle nature of light.

Question 44

A method for identifying a black hole is to

A) look for voids in the star fields.
B) look for their effects on nearby companions.
C) locate a visible star that disappears when the black hole passes in front of it.
D) search for radio waves from the accretion disk.
E) search for their pulsar signal.

Question 45

The key to identifying a black hole candidate in a binary system is that

A) one of the two stars cannot be seen.
B) the unseen companion in the system must have a sufficiently high mass.
C) the unseen star is a contact binary.
D) the system must be a very strong source of radio emissions.
E) the visible companion must be an evolving main sequence or giant star.

Question 46

If a spaceship travels near the speed of light away from the Earth, an observer on Earth would see the length of the spaceship ________.

Question 47

Something falling into a black hole will be ________ by tides.

Question 48

In M82, observations indicate that there are several bright sources close to the center of the galaxy. These might be

A) supernovae.
B) accretion disks of supermassive black holes, millions of times as massive as our sun.
C) accretion disks of intermediate black holes, hundreds of times as massive as our sun.
D) accretion disks of stellar mass black holes.
E) red giants in the process of forming planetary nebulae.

Question 49

On the surface of a sphere the shortest distance between two points is

A) an arc on a great circle.
B) a straight line.
C) a circle.
D) a triangle.
E) a curvy line.

Question 50

A ________ is a place where the current rules fall apart in science.

Question 51

General relativity explains gravity as the ________ of spacetime.

Question 52

The largest known black holes

A) create the dark nebulae in the plane of the Milky Way.
B) can be no more than 1.4 solar masses, according to Chandrasekhar.
C) lie in the cores of the most massive galaxies.
D) can be no bigger than a small city, just like neutron stars.
E) can be no bigger than the Earth, like white dwarfs.

Question 53

Which of the following is NOT an argument for Cygnus X-1's being a true black hole?

A) Spectroscopic data suggests hot gas is flowing from the companion B star onto Cygnus X-1.
B) The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses.
C) Cygnus X-1's mass is estimated to be about 10 solar masses.
D) X-rays from Cygnus X-1 vary on time scales as short as a millisecond.
E) X-ray observations around the object support a temperature of several million K.

Question 54

On a sphere, the interior angles of a triangle add up to ________ 180 degrees.

Question 55

The singularity of a black hole is

A) where general relativity predicts the density to be zero.
B) where the current understanding of gravity is incomplete.
C) the point at which nothing, not even light, can escape.
D) the region between the Schwarzschild Radius and the event horizon.

Question 56

What is Cygnus X-1?

A) The brightest star in the constellation Cygnus
B) The leading candidate for an observable black hole binary system
C) The strongest X-ray eclipsing binary system in the sky
D) A millisecond pulsar with three Earth-like planets around it
E) The first gamma-ray burster to be spotted in other wavelengths as well

Question 57

As a spaceship approaches the event horizon of a black hole, its radio transmissions would

A) be sucked into the black hole.
B) shifted to infrared or even visible light.
C) shifted to longer wavelength.
D) increase in amplitude.
E) be unchanged.

Question 58

If a specially designed space probe reaches the event horizon of a black hole, an observer watching the clock on this probe from a safe distance would see

A) the clock slow down.
B) the clock speed up.
C) the clock keep time in sync with the observer's clock.
D) the time on the clock would appear to change randomly.

Question 59

If the Sun were to magically and instantaneously be replaced by a 1 solar mass black hole, what would happen to the Earth's orbit?

A) It would be unchanged.
B) It would be much smaller, but its shape would be unchanged.
C) It would be at the same distance from the Sun, but would be much more eccentric.
D) It would be much larger, but its shape would be unchanged.
E) The Earth would be pulled into the black hole and destroyed.

Question 60

If a neutron star attains a mass over ________ solar masses it becomes a black hole.

Question 61

Why is the light from near a black hole redshifted?

Question 62

How is the Schwartzschild radius calculated?

Question 63

Relate escape speed to event horizon for a black hole.

Question 64

What are the three possible outcomes of stellar evolution? Describe each possibility, differentiating their means of formation and their subsequent properties. Which stars on the Main Sequence are thought to end up in each of these forms?

Question 65

Light from an object near the event horizon received by a distant observer is ________.

Question 66

Describe the properties of space in the vicinity of a black hole.

Question 67

What is some of the evidence that Cygnus X-1 is a black hole?

Question 68

The current theories of gravity are ________ because they do not incorporate a proper description of matter on the smallest scale.

Question 69

Relate escape velocity to the event horizon.

Question 70

How can a black hole of a few solar masses be detected?

Question 71

Explain how the essential features of special relativity imply that a beam of light from a fast moving spaceship will always be observed to moving at the speed of light.

Question 72

A black hole may be visible because electromagnetic radiation is emitted from an ________ surrounding it, heated up enough to emit X-rays.

Question 73

Special relativity says that time is a separate ________ in the workings of the universe.

Question 74

What happens to the size and mass of an object as it moves faster?

Question 75

To explain gravity, general relativity says that matter tends to ________ space in its vicinity.

Question 76

If you were to fall into a black hole, the ________ would kill you by tearing you apart.

Question 77

Why would the tidal forces around a black hole be of concern to a space explorer interested in investigating the area near a black hole?